1/* SPDX-License-Identifier: GPL-2.0 */
2#ifndef __X86_KERNEL_FPU_CONTEXT_H
3#define __X86_KERNEL_FPU_CONTEXT_H
4
5#include <asm/fpu/xstate.h>
6#include <asm/trace/fpu.h>
7
8/* Functions related to FPU context tracking */
9
10/*
11 * The in-register FPU state for an FPU context on a CPU is assumed to be
12 * valid if the fpu->last_cpu matches the CPU, and the fpu_fpregs_owner_ctx
13 * matches the FPU.
14 *
15 * If the FPU register state is valid, the kernel can skip restoring the
16 * FPU state from memory.
17 *
18 * Any code that clobbers the FPU registers or updates the in-memory
19 * FPU state for a task MUST let the rest of the kernel know that the
20 * FPU registers are no longer valid for this task.
21 *
22 * Invalidate a resource you control: CPU if using the CPU for something else
23 * (with preemption disabled), FPU for the current task, or a task that
24 * is prevented from running by the current task.
25 */
26static inline void __cpu_invalidate_fpregs_state(void)
27{
28 __this_cpu_write(fpu_fpregs_owner_ctx, NULL);
29}
30
31static inline void __fpu_invalidate_fpregs_state(struct fpu *fpu)
32{
33 fpu->last_cpu = -1;
34}
35
36static inline int fpregs_state_valid(struct fpu *fpu, unsigned int cpu)
37{
38 return fpu == this_cpu_read(fpu_fpregs_owner_ctx) && cpu == fpu->last_cpu;
39}
40
41static inline void fpregs_deactivate(struct fpu *fpu)
42{
43 __this_cpu_write(fpu_fpregs_owner_ctx, NULL);
44 trace_x86_fpu_regs_deactivated(fpu);
45}
46
47static inline void fpregs_activate(struct fpu *fpu)
48{
49 __this_cpu_write(fpu_fpregs_owner_ctx, fpu);
50 trace_x86_fpu_regs_activated(fpu);
51}
52
53/* Internal helper for switch_fpu_return() and signal frame setup */
54static inline void fpregs_restore_userregs(void)
55{
56 struct fpu *fpu = x86_task_fpu(current);
57 int cpu = smp_processor_id();
58
59 if (WARN_ON_ONCE(current->flags & (PF_KTHREAD | PF_USER_WORKER)))
60 return;
61
62 if (!fpregs_state_valid(fpu, cpu)) {
63 /*
64 * This restores _all_ xstate which has not been
65 * established yet.
66 *
67 * If PKRU is enabled, then the PKRU value is already
68 * correct because it was either set in switch_to() or in
69 * flush_thread(). So it is excluded because it might be
70 * not up to date in current->thread.fpu->xsave state.
71 *
72 * XFD state is handled in restore_fpregs_from_fpstate().
73 */
74 restore_fpregs_from_fpstate(fpstate: fpu->fpstate, XFEATURE_MASK_FPSTATE);
75
76 fpregs_activate(fpu);
77 fpu->last_cpu = cpu;
78 }
79 clear_thread_flag(TIF_NEED_FPU_LOAD);
80}
81
82#endif
83